1. Field of the Invention
This invention relates to a rear suspension system for a four-wheel-steered vehicle in which both the front and rear wheels turn in response to the rotation of the steering wheel.
2. Description of the Prior Art
Recently, there has been put into practice a four-wheel-steered vehicle in which both the front and rear wheels turn in response to the rotation of the steering wheel. Though the relationship between how the rear wheels turn and how the front wheels turn varies, generally, the rear wheels turn in a direction opposite to that of the front wheels when the turning angle of the steering wheel is large, that is, when the vehicle speed is low; and they turn in the same direction as that of the front wheels when the turning angle of the steering wheel is small, that is, when the vehicle speed is high. When the turning direction of the rear wheels is controlled in this manner, the turning radius at low speeds is minimized, and the running stability at high speeds is improved, as disclosed in U.S. Pat. No. 4,295,657, for instance.
When the rear wheels turn in the same direction as the front wheels, the turning angle of the rear wheels is very small, and accordingly, it must be accurately controlled.
In the four-wheel-steered vehicle, there has been a problem with the side force which acts on the rear wheels during cornering imparting a load to the tie rod and adversely affecting the accuracy with which the rear wheels turn.
Though the four-wheel steering system has contributed to the improvement of the running stability of the vehicle during cornering, up to the present it has not contributed to the improvement of the running stability during straight running, especially when the brake is applied.